.AixLib.Media.AirIncompressible

Information

This medium package models moist air using a gas law in which pressure and temperature are independent, which often leads to significantly faster and more robust computations. Additionally, the density is constant to improve the simulation stability and speed.

This medium uses the gas law

ρ = ρ_stp,

where p_std is a constant reference density.

The medium model can be used for air duct simulations, where the pressures and temperatures are close to the reference values.

Note that models in this package implement the equation for the internal energy as

u = h - p_stp ⁄ ρ_stp,

where u is the internal energy per unit mass, h is the enthalpy per unit mass, p_stp is the static pressure and ρ_stp is the mass density at standard pressure and temperature. The reason for this implementation is that in general,

h = u + p v,

from which follows that

u = h - p v = h - p ⁄ ρ = h - p_stp ⁄ ρ_std,

because p ⁄ ρ = p_stp ⁄ ρ_stp in this medium model.

The enthalpy is computed using the convention that h=0 if T=0 °C and no water vapor is present.

• January 09, 2020 by Alexander Kümpel:
  Copy from Air and density set constant

Contents

Name	Description
ThermodynamicState	ThermodynamicState record for moist air
BaseProperties	Base properties
density	Gas density
dynamicViscosity	Return the dynamic viscosity of dry air
enthalpyOfCondensingGas	Enthalpy of steam per unit mass of steam
enthalpyOfGas	Enthalpy of gas mixture per unit mass of gas mixture
enthalpyOfLiquid	Enthalpy of liquid (per unit mass of liquid) which is linear in the temperature
enthalpyOfNonCondensingGas	Enthalpy of non-condensing gas per unit mass of steam
enthalpyOfVaporization	Enthalpy of vaporization of water
gasConstant	Return ideal gas constant as a function from thermodynamic state, only valid for phi<1
pressure	Returns pressure of ideal gas as a function of the thermodynamic state record
isobaricExpansionCoefficient	Isobaric expansion coefficient beta
isothermalCompressibility	Isothermal compressibility factor
saturationPressure	Saturation curve valid for 223.16 <= T <= 373.16 (and slightly outside with less accuracy)
specificEntropy	Return the specific entropy, only valid for phi<1
density_derp_T	Return the partial derivative of density with respect to pressure at constant temperature
density_derT_p	Return the partial derivative of density with respect to temperature at constant pressure
density_derX	Return the partial derivative of density with respect to mass fractions at constant pressure and temperature
specificHeatCapacityCp	Specific heat capacity of gas mixture at constant pressure
specificHeatCapacityCv	Specific heat capacity of gas mixture at constant volume
setState_dTX	Return thermodynamic state as function of density d, temperature T and composition X
setState_phX	Return thermodynamic state as function of pressure p, specific enthalpy h and composition X
setState_pTX	Return thermodynamic state as function of p, T and composition X or Xi
setState_psX	Return the thermodynamic state as function of p, s and composition X or Xi
specificEnthalpy	Compute specific enthalpy from pressure, temperature and mass fraction
specificEnthalpy_pTX	Specific enthalpy
specificGibbsEnergy	Specific Gibbs energy
specificHelmholtzEnergy	Specific Helmholtz energy
isentropicEnthalpy	Return the isentropic enthalpy
specificInternalEnergy	Specific internal energy
temperature	Return temperature of ideal gas as a function of the thermodynamic state record
molarMass	Return the molar mass
temperature_phX	Compute temperature from specific enthalpy and mass fraction
thermalConductivity	Thermal conductivity of dry air as a polynomial in the temperature